OLED (Organic Light-Emitting Diode) display panels have the advantages of thinness, lightness, wide viewing angle, active luminescence, continuous and adjustable color of emitted light, low cost, fast response speed, small energy consumption, low driving voltage, wide working-temperature range, simple production engineering, high luminous efficiency, being usable for flexible display and so on, and have been listed as the next generation display technology having excellent development prospects.
Research shows that, water vapor, oxygen gas and similar components in air have a great effect on the lifetime of the OLED device in an OLED display panel, the reason is as follows. When an OLED device is in operation, electrons need to be injected from a cathode, and this requires the work function of the cathode to be as low as possible. However, the cathode is usually made of aluminum, magnesium, calcium or other metallic material, the chemical property of which is relative active, and which is very prone to react with water vapor and oxygen gas permeated therein; furthermore, water vapor and oxygen gas can also react with a hole transport layer and an electron transport layer in the OLED device; and all of these reactions can cause the failure of the OLED device. Therefore, by means of conducting an effective package for an OLED device so that functional layers of the OLED device are fully separated from water vapor, oxygen gas and similar components in air, the lifetime of the OLED device can be prolonged greatly, and thus the service life of the OLED display panel is prolonged.
At present, method for packaging an OLED device mainly includes: desiccant attaching plus UV adhesive coating, surface packaging, glass frit packaging, thin film packaging and so on. Packaging technology in which an adhesive dam and a filling adhesive are used belongs to the surface packaging. The filling adhesive has a higher transparency, so this packaging technology not only can be used for packaging of bottom-emission devices, but also can be used for packaging of top-emission devices, and is one of the packaging methods having excellent development prospects currently.
As shown in FIG. 1 and FIG. 2, an OLED display panel mainly includes a deposition substrate 19, an OLED device 16 located on the deposition substrate 19 and a protective layer 17 covering the OLED device 16, a package substrate 20 located above the deposition substrate 19 and disposed opposite to the deposition substrate 19, an adhesive dam 21 forming a sealed cell together with the deposition substrate 19 and the package substrate 20, and a filling adhesive 18 filled within the sealed cell. The adhesive dam 21 functions as a first barrier for blocking water vapor and oxygen, the filling adhesive 18 functions as a second barrier for blocking water vapor and oxygen, and the protective layer 17 not only has a function of blocking water vapor and oxygen, but also can prevent the filling adhesive 18 from directly contacting the OLED device 16 and thus affecting the operational characteristics of the OLED device 16.